The population structure of Monosporascus cannonballus, which causes vine decline in melons, was assessed based on the determination of mycelial compatibility groups (MCGs) in a collection of 58 isolates obtained from seven melon fields in three municipalities of Northeastern Brazil. For comparison, an additional 11 isolates of M. cannonballus from Spain were included in the analysis. MCGs were determined through comparisons of paired isolates growing on PDA culture media in the dark at 30ºC in various combinations. The Brazilian isolates were assigned into four MCGs: MCG-1 (n = 35 isolates), MCG-2 (n = 20), MCG-3 (n = 2), and MGC-4 (n = 1). MCG-1 and MCG-2 included isolates from all surveyed areas. The Spanish isolates were assigned into six different MCGs, and none of them were compatible with the Brazilian isolates. The genetic structure was determined using the frequencies of MCGs and genotypic diversity indices. The maximum genotypic diversity was 6.9 and 54.5% for the Brazilian and Spanish populations, respectively. The low level of genetic diversity in the M. cannonballus population from Northeastern Brazil suggests that breeding melons for disease resistance may be a promising strategy for the region.
Cucumis melo; melon; vine decline; soilborne pathogen; genetic diversity
